The present invention relates to a valve arrangement for regulating air in driers for foodstuff products.
Driers for foodstuff products at present use inlet and/or outlet air regulators including slide valves of the shutter or throttle type. Such valves receive an electrical actuation signal from processors or suitable electrical regulators, the electrical signal being transformed into movement of a pneumatic piston which reacts on the valve with relevant interposed actuating lever means.
Such arrangements have a number of disadvantages due to their particular design, the wear of components and the pneumatic actuation controlled by levers. They are subject to lack of accuracy in regulating the opening and/or closing, owing to the presence of levers and of the pneumatic actuation, and a slow operation of the electrical signal, owing to its transformation into pneumatic thrust.
In such known arrangements, owing to the presence of slideway guides, relevant seals, complications due to lever systems give rise to wear forces and/or imperfect regulation of the air passage, particularly under the high and variable operating temperature conditions present in driers. In addition, owing to the structure of the required means, the fitting to such driers in service, requires specific structural geometric shapes and, consequently, it is necessary to make numerous holes within the drier panels, with consequent considerable implementation costs.
In addition, the known regulation means must be suitably equipped with special securing plates, with consequent expense in the manufacture and location of such plates on the walls of the driers.
Yet another problem arises with the maintenance of all the components of the regulator arrangement, such as pneumatic pistons, lever systems, runner guides and seals which initially are also relatively expensive, in ensuring correct fitting to the drier.